Re: If I purchase sims 3 through steam, can I play through origin?
@itsmeeee4 Yes, it should absolutely be possible to transfer your game from Steam to Origin. Steam provides CD keys that you can register in Origin, and last I heard (maybe a couple of months ago), the process still worked fine.
If you're concerned about the keys not working, try to add them to your Origin account right away, and if they don't go through, request a refund from Steam. As long as it's been less than 14 days since you purchased, and you haven't played TS3 through Steam (or maybe played less than 2 hours, I'm not sure), you can get your money back. But it shouldn't be a problem—Steam is an approved vendor of EA games, including TS3.
By the way, all my TS3 packs are from Steam, and I've downloaded them via Origin a number of times, mostly for testing. It's never been a problem.